Harbor Freight Infrared Thermometer teardown

Infrared Thermometer

Item #93984

About a year ago I got one of these. Being the curious type I recently tore it apart to see if there was any way to interface it to a Microprocessor. Here are some pictures of the teardown.

Front

Back

Opened up

Closeup

Now were getting somewhere. The unit is a TN2 version 1.2A made by ZyTemp. Also note the header at the top. AGCDV. Looks promising.

Removed from case

 

 

 

 

ZyTemp has a website HERE. A quick look at the site show the TN2 listed as a TN205 HERE

Unfortunately the TN205 specs say nothing about the mysterious AGCDV header. Fortunately a further seach of the ZyTemp site yields this gem.

It's a TN901 infrared module and it seems to have a 5 pin header for output. I wonder of it is the same? Grabbing the user manual PDF we find that the header is labeled AGCDV just like my TN2.
Here's the text:
"3.4 Pin Assignment of TN0; TN9
Warning: The Dimension in this drawing is for reference only.
For actual dimension, please download from
http://www.ZyTemp.com/products/download/ExtDrawing.asp
V: Vdd G: GND
D: Data (Serial Data) C: Clock (Serial Clock)
A: Action Pin ( pull low to measure, floating while to Write Data into the IRT)
Note: TN0; TN9 has the same pin assignment."

 Cool. We now know what the pins do. Further research shows that it is some form of SPI interface and that the action pin causes the device to measure continuously if grounded. Time to get the pins out where we can work with them. Grabbing an old pc expansion card  I harvested a 5 pin header. I then soldered it to the TN2 board like so:













Then I needed to make a hole in the case so I could access the new pin header. Butchering the case with a pair of mini dykes gave me this:

After reassembly it still works!!

A cable from an old serial card gives me this:

 Now I'm ready to fire up my bus pirate and see what I can get out of it. Alas the unit's batteries are almost dead so I need to get some more before I can go on. Stay tuned for part II.